Abstract: In order to quickly and effectively determine the depth and continuity of the cutoff wall, and accurately locate the possible defects such as cracks and voids, it is necessary to find a more rapid and general detection method.In this paper, the resistivity contrast method was used for rapid detection, and the possible defect transverse area of the wall was found.Then, the resistivity CT method or the spontaneous potential method in the hole was used to accurately locate the abnormal position in the suspected abnormal area.The numerical simulation results of resistivity CT method show that resistivity CT has strong sensitivity to the defects of cutoff wall.At the same time, the combined method is less influenced by the reservoir water level and the ground detection conditions, and has strong applicability, which can provide a basis for the determination of engineering quality.